Centrifugal separators for particleladen gaseous media



y 29, 1956 w. R. CARTER 2,747,687

CENTRIFUGAL SEPARATORS FOR PARTICLE-LADEN GASEOUS MEDIA Filed Aug. 9, 1952 2 Sheets-Sheet l III 21705 WILLIAM RUPERT CARTER y 29, 1956 w. R. CARTER 2,747,687

CENTRIFUGAL SEPARATORS FOR PARTICLE-LADEN GASEOUS MEDIA Filed Aug. 9, 1952 2 Sheets-Sheet 2 WILLIAM Rupsar CARTER 63 United States Patent CENTRIFUGAL SEPARATORS FOR PARTICLE- LADEN GASEOUS MEDIA William Rupert Carter, Minneapolis, Minn., assignor to Superior Separator Company, Hopkins, Minn a corporationof Delaware Application August 9, 1952, Serial No. 303,594

1 Claim. (Cl. 183'77-)- This invention relates to machines and apparatus for efiiciently separating a gaseous medium from particles entrained thereby and contains several features of improvement over my co-pending applications, Serial Number 229,030, filed May 31, 1951, now Patent No. 2,109,500, and my co-pending application, Serial Number 300,743 filed July 24, 1952, now abandoned.

This application is a continuation in part of my (sopending, application, S. N. 300,743 filed. July 24,1952, particularly in the embodiment of thediminishing in diameter of the rotor periphery adiacent oneend thereof as by tapering or truncated conical construction to set upi-n. the driving of said rotor a velocity pressure lower at-the'diminished end.

As in my co-pending applications, it is an object to providepan exceedingly efficient gas separating machine or system which at high capacity will remove the finest particles of solid or other relatively dense materialentrained. in. a moving gaseous medium with resultant extraction of the gas in substantially a pure state. Genorally speaking, the invention utilizes centrifugal separation. and air separation? of denser and larger particles from the lighter gaseous medium through production of rapid. exterior and interior vortices of the particle-laden gas: in itsconstant flowthrough the machine or apparatus. Such functions are com'binat-ively associated with the withdrawal of the clean and separated gaseous medium through a relatively small withdrawal tube positioned axially and at one end of the inner vortex of the system. The vortices are set up through rapid revolution of a hollow, symmetrical rotor, being preferably densely apertured throughout at least the greater part of its peripheral wall. In the previous applications the air-or other gaseous mediums with the entrained, denser particles, travel generally through a helical whirling path from one end of the rotor to the other, resulting in continuous centrifugal separation of the solids and denser-particles from the gaseous medium throughout at the most, the length or height of the rotor.

It is an important object of the instant invention to provide in a centrifugal separator of the class described, mechanism and air flow controlling media and passages whereby the eifective lengths and areas of the separation vortices are-substantially doubled as contrasted with my earlier inventions, thereby materially increasing the capacity and efliciency of the machine and reducing power requirements for thedrivingof the rotor, and air circulating means.

Such highly advantageous results are achieved generally by a new combination and relationship of cooperating, parts including intake and clean gas discharge passages whereby the gaseous medium carrying entrained particles enters at one end of the rotor housing and is first caused to spiral rapidly along the outside of the rotor shell to the opposite. end thereof, setting up the exterioriseparation vortex and thereafter, entering the rotor essentially at said opposite end and spiraling within the rotor toward the. inlet end. of the housing, toset up the secondary or interior Patented May 29, 1956 vortex which is completely protected from outside turbulence by the revolving rotor. In this operation, continuous centrifugal. separation of the solid or denser particles from the light air or gas .takes place throughout the exterior vortex andin the general travel of the interior vortex with the gaseous. medium moving oppositely towards the intake end of the apparatus.

In my improved structure, the axial clean gas withdrawal tube is disposed at the same end of the rotor housing wherein particle-laden air or gas. enters.

It is a further object to provide a machine or apparatus of the class described wherein the problem of efliciently sealing the apparatus between the clean gas withdrawal tube and the interior of the rotor casing and/or rotor is materially simplified with nevertheless production of a more eificient rotor-centering seal.

Another object is to provide an air centrifuge or centrifugal air separating machine wherein the same structure may be utilized equally well without alteration onsystems where either suction or pressure creates the circulation through the machine or apparatus.

Still another object is the provision of a machine of the class described wherein through the shape of the rotor and its relation with intake and gas discharge optimum conditions are present for discharge of the solid or denser particles from the apparatus at a point of maximum distance from the point of gas withdrawal and wherein the solid material cannot fall into the clean gas withdrawal tubewhen the machine is idle.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters refer to similar parts throughout the several views and in which:

Fig. 1 is a View partly in side elevation and partly invertical section with portions being broken away, illustrating one form of my improved machine or apparatus;

Fig. 2 is a cross section taken on the line 22 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is a cross section taken on the line 3-3 of Fig. 1;

Fig. 4 is a view partly in side elevation and partly in vertical section with portions broken away, showing another form of my improved centrifugal separating machine;

Fig. 5 is a view partly in side elevation and partly in vertical section, with portions broken away, showing still another form of my invention; and i Fig. 6 is a cross section taken on the jagged line 6-6 of Fig. 5.

Referring now to the form of the invention shown in Figs. 1 to 3 inclusive, a cylindrical rotor housing 11 is employed being as shown, vertically disposed and having a smooth, internal, cylindrical wall, a top closure or disc 12 provided with a large axial air intake passage 12a and a bottom disc closure plate 13 which as shown, is supported in spaced relation to a horizontal supporting medium by spaced supporting legs 13a. The cylindrical housing and its closures 12 and 13 may be constructed of any suitable, relatively rigid material such as metal, composition material or plastic.

A relatively small, cylindrical air intake cap 14 is detachably affixed as by bolts 14a in axial relation to the top or upper end of the rotor housing, preferably having compressing attachment flanges 1411 which are sealed against the marginal edge of the top 12 which defines the intake opening 12a. Cap 14 is open at its bottom in smooth and open communication with passage 12a.

concentrically superimposed above the air intake cap 14 and rigidly supported. therefrom, isv a closed, cylindrical 'clean air or clean gas chamber 15a defined by an outwardly flanged cap member having a sealed top closure or disc 16 clamped with sealed elfect to the upper attachment flange 15b by suitable means such as bolts 17. Between the lower annular attachment flange 15c of the air discharge cap and the upper attachment flange 14c of the intake cap 14 is rigidly clamped by means of nutted bolts 18, a thick, horizontal annulus 19 which has firmly fixed in sealed relation or otherwise rigidly secured and sealed therewith, one race Ella of a double-sealed bearing indicated as an entirety by the numeral The inner race 20!) of the sealed bearing is fixed or otherwise rigidly secured and sealed around the upper and open end of a vertical, clean air withdrawal tube 21 which is axially disposed of the rotor housing ll and caps 14 and 15, extending upwardly into open communication with the clean air chamber 15a. Packing rings or gaskets 22 are interposed between the various attachment flanges of the caps 14 and 15 and the parts against which flanges are secured for sealing purposes.

Within the cylindrical housing 11 a hollow, generally cylindrical centrifuge rotor is mounted in spaced relation to the ends of the housing and also coaxially spaced with relatively wide clearance from the interior of the cylindrical housing shell 11.

This rotor, as shown, comprises a vertical shell, the upper and by far the greater portion of which is in the form of a very densely apertured, smooth rotor cylinder 2-3 surrounding at its upper extremity and being rigidly secured to and supported from an imperforatc, relatively thick disc 24 which is centrally apertured to snugly fit and be sealed with and secured to the exterior of the lower portion of the axial clean air withdrawal tube 21. The disc 24 as shown, is reinforced by an upper metal disc 24a and a lower, heavy ring 24b, ring 241; being preferably welded at its inner periphery in sealed relation to the withdrawal tube 21.

The lower portion of the rotor shell tapers downwardly towards the lower end of the rotor housing and as shown, is in the form of a truncated conical section 23a, the upper edge of which is welded or otherwise secured rigidly and smoothly to the lower end of cyl' l ical rotor portion 23. Section 2311 at its lower and diminished edge surrounds and is rigidly affixed to a lower imperforate closure disc 25 which constitutes the bottom of the rotor. The section like the larger a d upper cylindrical section 23 is preferably densely apertured and the apertures of both sections are of a dimension or dimensions to readily permit the largest size particles entrained in the entering air or gaseous medium to very freely pass therethrough during rapid revolution of the rotor. The apertures may be circular, oblong or diamond shape or any of the other shapes as disclosed in my co-pending application, Serial Number 300,743.

Both external and internal surfaces of the centrifuge shell, constituting sections 23 and 2311 are smooth and unobstructed by ribs, corrugations or dctents in my preferred form.

The outer race 26a of a double-sealed bearing 26 is aflixed to and sealed against the bottom 13 of the rotor housing, being coaxial with the rotor and related with the inner race 26b of the complete bearing 2'6. Inner race 26b is alfixed in sealed relation to the lower portion of the rotor shaft 28. The sealed bearing 26 takes the thrust of the vertical rotor and acts as a seal between the rotor and the bottom of the rotor housing. A lower scouring disc 27 densely apertured similarly to the shell of the rotor, is rigidly affixed to the outer and revolving bearing race 26a and disposed in close working clearance to the bottom 13 of the housing and being of a diameter of equal or slightly larger dimensions than the maximum diameter of the rotor shell 23.

The rotor shaft 23 is rigidly aflixed at its upper portion to the clean gas withdrawal tube 21 by means of an upper spider 29 and a lower spider 3%, said spiders positioning shaft 28 axially of withdrawal tube 21 and rotor sections 23 and 23a. The lower portion of rotor shaft 28 is rigidly aflixed to and passes through the bottom closure disc 25 of the rotor projecting through an aperture in the inner bearing race 26b and having as shown, a squared drive connection extremity 28:: which as shown, is operativcly connected with the squared socket 3-1 of a flexible driving shaft connected with a suitable source of high speed rotary power.

Sealed bearings of the type utilized for thrust bearing 26 and the upper bearing 2d, are supplied by several manufacturers, in several instances having double-sealed both the top and bottom of the bearing races. It will of course be understood that various bearings which provide for smooth and substantially frictionless revolution of the withdrawal tube 21 and the rotor rigidly connected therewith and preferably which have a self-centering factor, may be used. it is imperative that the bearing construction at the upper end of the apparatus be of such nature that perfect seal is formed between the relatively stationary and rotating parts so that there may be no leakage of gaseous medium or fine particles from the interior of the intake cap 14 into the clean" gas discharge chamber 35a.

The annular space between the periphery of the rotor and the cylindrical housing 11 forms a particle-receiving chamber 32 wherein the exterior, rapid vortex of gaseous medium with entrained particles is set up in the flow, said vortex spiraling downwardly to the lower end of the rotor. A suitable air-lock, particle-discharge structure is mounted at one side of the rotor housing 11 and at the lower end thereof for controlling and facilitating uniform discharge of the separated, denser particles. This air-lock structure is encased in an upstanding, generally cylindrical housing 33 having open communication substantially the full height thereof with the lower portion of housing 11 and extending to the bottom closure 13 of the housing. A rotary air-lock member 34 affixed to a short, vertical shaft 34a is suitably journaled in the top and bottom of housing 33 and as shown, is provided on its periphery with relatively deep, longitudinal fiutings 3412 which form with the cylindrical, upstanding portions of housing 34 chambers for receiving and moving quantities of particles from within the lower part of the rotor housing. The orbit or path of the longitudinal edges of the flutings 34b extends slightly inwardly beyond the inner periphery of the cylindrical housing shell 11 to provide in operation, a scraping or cutting-off action of particles collected within the rotor housing. Housing 33, at its side opposite its attachment to the rotor housing, is provided with an elongated discharge passage, the full height of member 34 which as shown, communicates with the upper end of a particle discharge chute 35. The structure of my particle-removing air-lock is similar to that disclosed in my co-pending application, Serial Number 300,743 and further detailed description thereof is thought unnecessary. Air-lock member 34 is driven at relatively slow speed as contrasted with the R. P. M. of the rotor and as shown, has affixed to the lower end of air-lock shaft 34a, the connection socket 36 of a flexible driving element which in operation is connected with a suitable source of rotary power.

In the embodiment of the invention shown in Figs. 1 to 3 inclusive, a large supply duct 37 is connected in radial relation with the interior of the intake cap member 14 to convey the particle-laden gaseous medium to the intake of my machine. Also, as shown, a tangentially arranged discharge duct 38 is connected with the upper cap member 15 in communication with the chamber 15a therewithin. Flow may be set up through may apparatus either by pressure or suction system. For example. the discharge duct 38 may be connected with the intake of a blower which discharges the clean air or other gaseous medium to desired points. Or, the intake duct 37 may be connected with the discharge of a blowerwhich supplies and forces the particle-laden air into the' intake of my machine. Where my apparatus or machine is utilized with a pressure supply system and it is desired to discharge the cleaned air or gaseous medium into the atmosphere surrounding the machine, the top cap and duct 38 of my apparatusmay be eliminated and the upper end of clean withdrawal tube 21 and the sealed bearing may be covered with a suitable grill or grate.

Operation In operation, the centrifuge rotor'is driven at relatively high speed, varying within a range (depending upon the nature of the use) all the way from a peripheral, linear-foot-travel of from 5000' feet per minute .up to 15,000 feet per minute. The higher speeds are utilized for centrifugally extracting smaller and less dense particles from the gaseous medium. Continuous flow of the particle-laden air or other gaseous medium is provided as previously stated, by connecting the system with either a pressure or suction source of circulation. The particleladen air is always introduced through the annular cham ber defined by the intake cap member 14- in conjunction with the exterior of the sealed clean gas withdrawal tube 21.

The entering gaseous medium with its entrained particles passes downwardly through the relatively large. central and annular passage 12a in the top of the rotor housing and is driven spirally by the rapidly revolving, cylindrical rotor having the densely apertured peripheral shell. A substantially uniform distribution of the entering medium radially and tangentially of the upper end 24 of the rotor is effected through the deflection effect of the rotating upper end 24. Thus, the particle-laden gaseous medium forms a rapid vortex surrounding the rotor shell and this vortex because of the how of the apparatus, spirals downwardly'to the lower and diminished or truncated conical end of the centrifuge rotor. in the downward spiral movement of the gaseous medium, the denser and larger particles such as solids are thrown outwardly by centrifugal force, collecting and working their way downwardly in the annular chamber 32 while simultaneously at the lower portions of the rotor shell, the light gaseous medium or air Works its way inwardly through the apertures in the rotor shell.

The velocity pressure area is lowest at the lower portion of the annular chamber 32 surrounding the downwardly diminished tapered or truncated conical lower portion 23a of the rotor shell. Consequently, the whirling gaseous medium readily enters this portion of lowered velocity pressure to a substantial extent through the apertures formed in the lower section 23a of the rotor shellv and in the apertures of the cylindrical portion just above said diminished section. The diminishing of the lower end of the rotor further provides maximum clearance in the annular passage 32 with attendant advantages in connection of particle-removing means at such portion. The gaseous medium enters the lower section 23a through its apertures radially inward and somewhat in. a longitudinal, upwardly directed manner and such gaseous medium still may contain a considerable percentage of the finer and less dense solid particles. Such entering gaseous medium through the rapid driving effect of the interior of the hollow-apertured rotor forms a very uniform interior separation vortex and spirals upwardly towards the intake end of the rotor housing. In such upward sprial travel the finer, relatively dense solid and other particles are centrifugally separated, moving outwardly against the interior of the cylindrical portion 23 of the rotor and passing through the relatively large apertures therein and the intake end of the housing and then secondly, by F the opposite moving upward spiral of the interior sepa= ration vortex towards the upper end- 2 40f the rotor. The interior and upwardly moving vortex is shieldedagainst outside effects of' turbulence and eddy currents bythe symmetrical, smooth surfaced rotor shell comprising sections 23 and 23a. The increase of the angular velocity of the gaseousv medium, ignoring friction losses, from the periphery of the internalvortex towards the axis thereof and toward the open lower end of clean gas withdrawal tube 21, is inversely proportional to the diameter of the vortex, with the result that the most effective centrifugal action upon particles of greater density and size than the air or other gaseousmedium, is effected in the central area surrounding and below the open end of the air withdrawal tube 21. Very nearly a ef ficiency in separation of pure gaseous medium from the entrained particles is thus effected with my structure.

The forced flow by suction or pressure of the gaseous medium through the system and structure causes the withdrawal of the separated and clean gaseous medium upwardly and axially through the open ended discharge tube 21 which preferably projects at its inner end for some distance below the upper end 24' of the rotor.

The flow through the system with the downward spiral vortex surrounding the exterior of the rotor shell causes the denser particles to be thrown and collect in the peripheral or outer strata of the exterior vortex, working downwardly to thebottom' of the rotor housing 11'. The accumulating particles are constantly and at a uniform rate, engaged by the ribs of the flutings 34b of the airlock discharge and by cutting or scraping action, these denser particles are constantly removed and discharged from the apparatus through the. chute 35 without disturbing the pattern .of the vortex and without creating fluctuations in the pressure area at the lower portion of the rotor housing.

The hollow centrifuge rotor because of its relation with the intake of the particle-laden gaseous medium and with the axial clean gas withdrawal tube 21 axially disposed through the intake portion of the system, effectively drives and sets up oppositely moving exterior and interior separation vortexes, thereby providing a separation area or length substantially twice that available in my earlier inventions. lnthis connection, it is essential that the upper end of the rotor be closed and substantially imperforate with .at least provision for excluding travel of all gaseous medium longitudinally into the upper end of the rotor.

The inverted, truncated conical section 23a at the lower end of the rotor shell, substantially facilitates the turning and reverse travel of the swirling gaseous medium with the attendant production of the rapid interior separating vortex on a spiral path moving upwardly within the confines of the rotor. While the diminished or downwardly tapering section 23m of the rotor is shown in the form of a truncated cone, it is of course recognized and applicant has ascertained that other suitable, tapered geometrical figures for section 23a of the rotor shell may be utilized as equivalencies provided the taper or diminishmen-t is progressive from the intermediate, cylindricalportion towards the end of rotor 23- opposite to that wherein withdrawal tube A is mounted.

Referring now to the form of the invention illustrated in Fig. 4, the structure and relationship of the particleladen gas intake cap and chamber 14, the top 12 of the rotor housing, the clean air withdrawal tube 21 and the clean air or gas chamber 15a defined by the upper cap member 15 and the air-lock casing 33 and air-lock structure therewithin are all identical to the form of the invention first described and therefore are correspondingly numbered on the drawings. An identical, doublesealed bearing lit, the outer race of which is aihxed to the heavy annulus I9, is utilized in this second form of the invention.

The symmetrical shell or body of the rotor housing.

however, is different and in the form of Fig. 4, comprises an inverted, elongated, truncated conical casing 40 which tapers uniformly as shown, from its upper to its lower end. The bottom closure 49a for the housing is connected in sealed relation with the lower end of casing 46 and as shown, is supported on legs 49b. The rotor of this second form of the invention comprises a densely perforated, continuous inverted frustoconical shell 41 tapering uniformly from its upper to its lower end and as shown, tapering somewhat more sharply than the rotor housing 40 to afford in its spaced concentric relation with the housing, increasing clearance between rotor and housing from the upper end of the device to the lower end thereof.

The rotor shell 41 may be densely apertured in any of the manners recited with reference to aperturing of rotor sections 23 and 23a of the form first described. The upper end of rotor 41 is closed by a disc 24 and reinforcing elements 240 and 24b identical with the upper closure for the rotor of the first form of the invention and the withdrawal tube 21 is rigidly aflixed by rotation to the rotor by spiders 25 and 30, said spiders being affixed to the rotor shaft 28 which has aflixed to the lower end thereof below the closed imperforate bottom disc 44 of the rotor, a collar 45 which has attached to the underside thereof a scouring disc 27 identical with the scouring disc of the first form of the invention. The rotor shaft 28 extends through the bottom closure 4th: of the rotor housing and is somewhat diminished for fixed and sealed connection with inner bearing race 46b of a double-sealed bearing 46 having the outer race 46a thereof supported in a depending, internally flanged collar 47 secured centrally to the bottom 40a of the rotor housing. The rotor shaft as shown, depends from the bearing 46 and is driven by a flexible shaft 48 from a suitable source of power.

While in Fig. 4, the rotor housing or casing 46 is gradually tapered throughout its length from top to bottom, 1 have obtained equally good results with the rotor 41 of the structure shown in Fig. 4 combined with a rotor housing of cylindrical shape such as is shown in Fig. l.

The uniformly tapered or diminished rotor 41 is preferred to the form of rotor shown in Figs. 1 and 5. Careful tests have shown that in any event it is highly important to produce substantial entrance of the gaseous medium at the lower end of the rotor with attendant upward spiraling within the confines of the rotor, that a reduced velocity pressure area be set up or present at the lower end-portion of the rotor.

The form of the invention shown in Fig. employs a cylindrical rotor housing 50 having a removable cap closure designated as an entirety by the numerals 51, said closure as shown having an overlying flange 51a which is adapted to surround the upper extremity of the cylindrical housing 50. The upper end of housing 50 internally and rigidly carries an axially disposed, up-

wardly flaring skirt 52 communicating with the interior or dome of cap member 51 and terminating at its lower end in a tubular clean gas withdrawal medium 52a which is disposed axially of the housing 50 and the rotor mounted therein and which preferably extends at least a short distance below the upper end of the rotor. The skirt 52 and withdrawal tube 520 in this form of the invention are stationary and serve to support and center the upper end of the rotor 53. To this end, a double-sealed thrust bearing 54 of a structure similar to the scaled bearings previously described or any other suitable structure is utilized having the inner and stationary race 54a thereof rigidly aflixed to the medial portion of withdrawal tube 52a and sealed against the outer periphery thereof and as shown, disposed just above the top, imperforate closure disc 53a of the rotor 53. The outer race 54b of the sealed bearing at its lower edge, is secured to and elliciently sealed against the inner marginal edge of the top or upper closure disc 53a of the rotor. The sealed bearing 54 is provided with the conventional sealing shims or means disposed at top and bottom thereof between the races 54a and 54b. If desired, an additional protection skirt 55 may be aflixed to and sealed with the intermediate portion of skirt 52 flaring outwardly at its open lower end and surrounding the bearing 54 and through its sealed connection with skirt 52, forming a dead air space surrounding and above said bearing.

Rotor 53 is densely perforated with apertures which may be formed of various shapes and within the range of dimensions previously specified for the apertures of rotors previously described. The rotor 53 of this form of the invention does not utilize an axial rotor shaft but the space therewithin is entirely unobstructed and the lower closed end 53b of the rotor is affixed to and sealed with the lower truncated conical section 53c, of the rotor, being reinforced by a flanged collar 56 which is secured to a lower stub shaft 57 which passes through the closed bottom 50a of the rotor housing and is journaled in a suitable sealed bearing 58, the outer race of which is affixed to and sealed with the central bottom portion of closure 50a. Stub shaft 57 projects downwardly below the bearing 58 and as shown, is driven by connection with a flexible driving shaft 59.

An air-lock structure generally similar to the air-locks previously described for uniform discharge and removal of collected particles is provided, comprising a housing 69 having vertically mounted therein, a central shaft 61 upon which a discharge rotor is centrally affixed, said rotor as shown, comprising a plurality of circumferentially spaced blades or edges 62 having therebetwecn fluted recesses 62a. The blades 62 are positioned to have their outer longitudinal edges disposed just inwardly of the confines of the cylindrical housing 53 during the revolution thereof to scrape or cut off segments of the accumulating particle-collection within the lower portion of the housing. The air-lock is driven as shown by connection of the lower end of shaft 61 with a flexible driving element 63.

An intake passage is formed tangentially with respect to the upper portion of the housing 50 and as shown (see Figs. 5 and 6) is connected with an intake duct 64. The cap or dome member 51 as shown, is provided with a tangentially disposed clean gas discharge passage communicating with a duct 65. The said ducts 64 and 65 and said passages are related with the housing and cap 51 to facilitate the continuous spiraling of the gaseous medium in the flow of my machine and in the direction of revolution of the rotor.

In the several forms of the invention disclosed, there is a close combinative relationship between the shape and construction of the rotor diminished progressively at its lower end or its end opposite from the disposition of the axial gas withdrawal tube. With the relationship of intake for particle-laden gas and axial withdrawal of the clean separated gas, highly efficient results may only be obtained where at least the said lower portion of the rotor shell is tapped or diminished towards its lower extremity and where that diminished portion is provided with at least one zone of said apertures. The tapering rotor or end portion of the rotor is responsible for production within the rotor housing adjacent thereto, of lower velocity pressure and consequently entrance of the downwardly spiraling gaseous medium into the rotor with subsequent upward spiraling of said medium therein, is very substantially facilitated by the shape of the rotor in combination with the other essential parts and passages of my device.

It will of course be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of my invention.

What I claim is:

A centrifugal separating machine for removing particles from a particle-laden gaseous stream comprising,

a separating chamber through which the moving gaseous stream is passed, a power-driven rotor of hollow, symmetrical construction mounted within said chamber in spaced relation to the walls thereof to provide an annularly arranged, first stage, centrifugal separation chamber, said chamber having a gaseous stream inlet adjacent one end thereof, said rotor having a densely foraminated peripheral wall of circular cross section defining interiorly an unobstructed passage for substantially the full length thereof to permit simultaneous radial and axial move ment of the gaseous stream through the rotor and with the foraminations of such size as to freely permit passing of particles radially in either direction during rotor revolution, said foraminated wall being adapted in revolution to set up a first stage, exterior separation vortex and a second stage interior separation vortex, said rotor having an imperforate, annular end portion substantially closing one end of said peripheral wall and disposed adjacent said stream inlet to direct incoming flow radially outward about the periphery of said rotor, a clean gas withdrawal tube of substantially smaller diameter than said rotor connected at its outer end with gas withdrawal means and having an inner open end extending axially within the interior of said rotor through said annular, imperforate rotor end portion and having a sealed relation with said portion, said inner end of said tube functioning to concentrate the apex of said inner separation vortex axially of said imperforate end portion of the rotor whereby with said exterior, first stage separation vortex, the particle-laden gaseous medium passes in a vortex-like path from adjacent one end of said rotor towards the opposing end, then enters the interior of said hollow rotor and reverses its direction to pass in the secondary spiral vortex-like path towards the inner end of said clean gas withdrawal tube and in its opposite spiral travel the angular velocity of the stream increases with the decrease in diameter of the path to subject the remaining particles carried by the stream to an increasing centrifugal force, thereby separating the particles from the gas and centrifugally directing the particles radially through said foraminations to the space peripherally of the rotor for discharge, the end portion of said rotor opposite from the recited imperforate end portion diminishing in diameter to its extremity whereby velocity pressure within said chamber is lowest about said diminished end portion to facilitate spiral travel of the gaseous medium in the external vortex towards said diminished end portion of flow of said gaseous stream through and into said rotor at said diminished end portion.

References Cited in the file of this patent UNITED STATES PATENTS 602,964 Van Gelder Apr. 26, 1898 1,954,352 Dornbrook et a1. Apr. 10, 1934 2,085,506 McKeOWn June 29, 1937 2,507,335 Donohue May 9, 1950 2,530,112 Arnold Nov. 14, 1950 2,546,558 Niederkorn Mar. 27, 1951 FOREIGN PATENTS 4,227 Great Britain Mar. 19, 1888 380,680 Germany Sept. 11, 1923 382,752 Germany Oct. 5, 1923 410,864 Germany Mar. 23, 1925 711,622 Germany Oct. 9, 1941 

